On the behaviour and ecology of the Black-tailed Godwit

Migration: The large variation in the migration of godwits is mostly the result of consistent differences between individuals. These differences are large compared to other migratory bird species. The survival of godwits during migration is also higher compared to other bird species. The mortality that does occur on migration is mostly the result of adverse wind conditions during northward Sahara crossings.The considerable variation in the migration of godwits might therefore result from an absence of a consistent selection pressure during migration. The consistent differences among individuals develop during multiple years of life. A translocation experiment to Poland with naïve juveniles from The Netherlands showed that the development of their migratory direction and wintering location was not merely inherited. Polish individuals are less consistent in their migration than those from The Netherlands. This might be because there is less canalization through social factors in the lower density Polish population. Population: Godwits are monogamous, but do sometimes lay eggs in the nests of other godwits. Individuals lay similarly sized eggs every year. Our traditional observation methods often fail to capture the first nest and the renests of individual godwits. This observational bias has led to biased estimates in the past. Even though the sex ratio at hatch is equal, higher survival of male chicks and adults leads to a surplus of males. Sexual dimorphism develops during the chick phase in godwits and needs to be accounted for when evaluating the condition of chicks.